Reflections of my thoughts….

For doing this, we can make use of WM_CTLCOLOR message OnCtlColor function.
If you add a handler for the above message, Windows will draw with the brush you are creating inside this function.
Before drawing childe controls, this function will be called(for certain types. refer MSDN for more info). nCtlColor parameter will only provide the type of child control. If we have three edit box named red, green, blue, and if we need to give different back color for each item, we can differentiate the controls by getting it’s ID. we can get the child control’s ID by calling GetDlgCtrlID() function of the window pointer passed to this function. The following code decribes how to implement the same.

You can use the same technique for buttons, static control and other controls supported by this message. Full list of controls is available in MSDN.

Sample Code:

HBRUSH CSampleDialogDlg::OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor)
{
	HBRUSH hbr = NULL; // Initialize with a NULL brush

// Execute for edit box only
	if(CTLCOLOR_EDIT == nCtlColor)
	{
		COLORREF clrBack = RGB(0,0,0);

int nCtrlID = pWnd->GetDlgCtrlID(); // Get the control ID

		if(IDC_EDIT_RED == nCtrlID) // if edit blue
			clrBack = RGB(0xFF,0,0); // Red back color
		else if(IDC_EDIT_GRN == nCtrlID) // if edit green
			clrBack = RGB(0,0xFF,0); // Green back color
		else if(IDC_EDIT_BLUE == nCtrlID) // if edit blue
			clrBack = RGB(0,0,0xFF); // blue back color

hbr = CreateSolidBrush(clrBack); // create brush with selected color

pDC->SetBkMode(TRANSPARENT); // little more tweak make the draw transparant

}
	else // default brush
	{
		hbr = CDialog::OnCtlColor(pDC, pWnd, nCtlColor);
	}

return hbr;
}